Generation of induced pluripotent stem cells (iPSCs) from somatic cells through cellular reprogramming offers tremendous potential for therapeutics, the study of disease states, and elucidation of developmental processes. Central to the process of generating a pluripotent cell from a somatic cell is an energy-dependent epigenetic reconfiguration event that must occur to produce iPSCs with characteristics similar to embryonic stem cells. However, the identity of nuclear factors that activate the metabolic programs linked to pluripotency and their contribution to epigenetic reprogramming remains largely unclear. Our lab is known for its discovery of the family of nuclear hormone receptors (NHRs) that use hormones to control genes and thereby regulate embryonic development, physiology and metabolism. Utilizing our specialized NHR knowledge and tools we identified a sub-population of cells that arise early in reprogramming that transiently express the NHR Estrogen Related Receptor alpha (ERRα). These rare cells provide the principal reservoir from which iPSC cells are produced.
Utilizing this newly identified cell population, we will determine the metabolic pathways during cellular reprogramming that reestablish ES cell-like chromatin patterns. Understanding the mechanism of epigenetic resetting could be exploited to deal with adult diseases such as cancer or even in ‘rejuvenating’ aged cells.

Statement of Benefit to California:

Our focus is on nuclear hormone receptors (NRs) that use hormones to control genes that regulate development, growth, and physiology. This has brought in more than $100M in private and federal funding to this lab over the last 30 years and has led to employment of 150+ people, publication of over 350 papers, and founding of three biotech companies that in aggregate raised more than $1B in research and development support. Several FDA-approved drugs for cancer, diabetes, osteoporosis, and leukopenia were developed with this technology. We found that a unique subset of 38 NRs are expressed in adipose-derived human induced pluripotent stem cells (hiPSCs), but little is known of how they control stem cell renewal and differentiation. Potential use of the extensive family of hormonal ligands to control iPSC generation, maintenance, and cell fate has profound implications for regenerative medicine. We wish to use our expertise to understand how NRs can be exploited to accelerate the use of iPSCs in regenerative medicine. Our proposed study should be beneficial to the State of California and its citizens in several ways: 1) by maintaining a unique training environment for students, postdocs and physicians; 2) discovering how to more efficiently generate and use human iPSCs; 3) deciphering the molecular genetic logic of nuclear reprogramming; 4) determining how a pharmacopeia of hormones and drugs can be brought to bear on directing stem cell renewal, differentiation, and therapy.

Review Summary:

This Fundamental Mechanisms Track application intends to uncover the mechanisms that regulate the estrogen related receptor (ERR) and its cofactors that form a transient, high-energy state during cellular reprogramming. To achieve this goal, the Principal Investigator (PI) proposes three aims. First, the PI will perform a molecular characterization on a specific transiently expressing ERR to link molecular mechanisms between the high-energy state and epigenetic reprogramming. Then, the PI will determine the role of ERRs in generating iPSCs. Finally, the PI will investigate epigenetics dynamics that occur during reprogramming.

Significance and Innovation
- The proposal focuses on the regulatory mechanisms that govern changes in cellular metabolism during transcriptional and epigenetic reprogramming. This will expand our understanding of human stem cell behavior and properties.

- The PI has identified a role for the ERR in cellular differentiation and maintenance.

- The PI has identified a population of cells that are enriched and metabolically mature.

- Reviewers suggested that the PI show more evidence of the proposed role of cellular metabolism in establishing and maintaining pluripotency.

Feasibility and Experimental Design
- The proposal is well written, logical and well organized.

- There is an impressive amount of compelling preliminary data to support the hypotheses.

- Reviewers noted that the PI has done knockdown experiments, but still gets 30% reprogramming in these studies. Thus, the reviewers commented that for the PI to conclude that this is an essential factor may be an overstatement.

- Reviewers voiced minor concerns regarding what the next step the PI would take after the proposed experiments are completed.

Principal Investigator (PI) and Research Team
- The PI is a world leader in the field of nuclear hormone receptors and cellular metabolism.

- The PI publishes outstanding papers in top tier journals.

- The PI has recently begun to work in the area of stem cells and reprogramming.

Responsiveness to the RFA
- The proposal describes the study of mechanisms to better understanding reprogramming and is responsive to the RFA.